Generally, the mechanical reinforcement to external factors, such as a rainstorm, of the radar antenna currently installed out in the fields is inadequate. However, a part for an antenna element section is used in the state where it exposed. As the reason, in order to protect a part for an antenna element section from breakage by external factors, such as a rainstorm, and Since mechanical strength of an antenna is increased, when a reinforcing member for reinforcing a part for an antenna element section is attached to a part for an antenna element section, it is for radio wave loss to arise on a radio wave which enters into an antenna, and for the directivity of an antenna to deteriorate by this reinforcing member.
Then, in order to protect antenna elements, such as a radar, the radome with which the whole antenna is covered is used. This radome is formed in the shape of a globular form, a cylinder type, a rectangular parallelepiped form, etc. by a skeleton member. The surface of this skeleton member is covered with surface protection material, and is protected. Generally, as surface protection material, dielectric plates, such as FRP (fiber reinforced plastics and the following describe it as FRP) which is radio wave penetration material, are used. As for the skeleton member of the radome, aggregate or metal is used.
Aggregate is manufactured with the dielectrics which have the same character as FRP. As an antenna device which uses the sphere lens represented by the Luneberg lens, there is antenna device 111 shown in FIG. 13. Antenna device 111 consists of sphere lens 114, radome 133, and foam material layer 134. Foam material layer 134 is filled up with a foam material between sphere lens 114 and radome 133, and is formed in it. This foam material layer 134 has combined sphere lens 114 and radome 133. Sphere lens 114 is held by foam material layer 134 in radome 133.
[Patent documents 1]
JP, 2001-102857, A